I am looking for the most appropriate dataset for downloading baseline gene expression level across all human coding genes during development. I am aware that EMBL Expression Atlas is one of the resources that provide such information, but I am ideally looking for species averaged (and probably scaled) expression data for all human coding genes during early stages of development! Any insight is much appreciated!
There is not going to be a public database with this data. Apart from anything else, generating data for early human development is difficult and ethically tricky. Also, most people who care about development would probably think that a whole body average would be meaningless.
The best you could do would be to select tissues you were interested in from something like Expression Atlas and calculate the averages yourself.